There exists a desire reduce critical dimensions of features in products. As the features decrease in size, the impact of contamination during processing of the features increases, which may produce defects. Exemplary contaminants are particulates that include polysilicon slivers, photoresist particles, metal oxide particles, metal particles, slurry residue, dust, dirt, as well as various elementary molecules such as carbon, hydrogen, and/or oxygen. Particulates frequently adhere to a surface by weak covalent bonds, electrostatic forces, van der Waals forces, hydrogen bonding, coulombic forces, or dipole-dipole interactions, making removal of the particulates difficult.
Historically, particulate contaminants have been removed by a combination of chemical and mechanical processes. These processes employ cleaning tools and agents that have a probability of introducing additionally contaminants during a cleaning process.
Another technique for cleaning substrate surfaces omits the use of chemical agents by exposing the surface to high heat in to vaporize contaminants present thereon. The vapors are removed by evacuating a chamber in which the surface is present. The high temperatures required for this process limits its application to post deposition processes not involving material having a structure that varies at temperatures proximate to the vaporization temperature of the contaminants.
Another cleaning technique is disclosed in U.S. Pat. No. 6,881,687 and employs a laser-clean yield-enabling system. The system incorporates a laser cleaning operation working in conjunction with a defect inspection operation cooperating to feed information regarding the root cause of the remaining defects back to earlier process stages, for correction of the root causes, with resultant improvement in yield. In a simplest configuration, the particles remaining after a laser cleaning would be characterized as to their types, sizes, shapes, densities, locations, and chemical compositions in order to deduce the root causes of the presence of those particular particles. This information is used to improve the yield of subsequent product wafers being processed so that their yields are higher than the wafers characterized. It is desired, however, to provide a more robust cleaning process that avoids the presence of particulate contaminants remaining on the surface that has been subjected to a cleaning process.
Therefore, a need exists to provide improved techniques to clean substrate surfaces.